Toxicological evaluation of chemicals/materials that may affect human health is an important aspect of public health research. The purpose of this contract is to support the National Toxicology Program (NTP) in its efforts to identify and assess chemical agents potentially affecting human health through environmental exposure. This contract provides information on comprehensive chemical characterization, purity determination, confirmation of administered dose levels, and internal dose determinations. This information is critical for sound and scientific conclusions and supports the risk assessment efforts of NTP and other federal agencies. With internal dose information provided by this contract, extrapolations to humans can be made so that the public can be adequately informed about risk factors associated with the exposure with these chemicals. A wide variety of chemicals/test articles are studied by NTP, for example: solvents, plasticizer, flame retardants, dietary/herbal supplements, and sunscreen. The chemistry support contract provides NTP with chemical procurement, dose formulations and analysis, bulk chemical comprehensive analysis of bulk material, along with biological sample method evaluation as well as studies to determine internal dose and other toxicokinetic parameters.